Recent JLab Spin Data

1
Recent JLab Spin Data
RHIC AGS Annual Users' Meeting Longitudinal
Spin Workshop
Karl J. Slifer University of New Hampshire June
1, 2009
2
This Talk

• Existing g1p data
• BurkhardtCottingham Sum Rule
• What does the JLab data tell us?
• Is it enough to make a definitive statement?
• Higher Twist Measurements
• Target Mass Corrections
• Spin Polarizabilities
• Future Experiments

3
CWLinear Accelerator 3 Exp. Halls 0.1 nA to
200 ¹A Pb 85 6 GeV Max Energy
4
CWLinear Accelerator 3 Exp. Halls 0.1 nA to
200 ¹A Pb 85 6 GeV Max Energy
A
C
B
12 GeV upgrade 2012
5
Halls A and C

• High Momentum Spectrometer (HMS)
• Max momentum 7.5 GeV
• Resolution 10-3
• 18 momentum acceptance
• Angular acceptance gt 6msr
• Short Orbit Spectrometer (SOS)
• Max momentum 1.8 GeV
• Resolution 10-3
• 40 momentum acceptance

C
A
High Resolution Spectrometers (HRS) 10-4
Resolution Momentum 0.3-4.3 GeV/c Max L
1038cm-2s-1 Anglular acceptance ¼ 4msr
6
Hall B
CLAS Six-coil toroidal field large kinematical
coverage central field-free region Almost 4¼
coverage Reduced luminosity
7
Target Polarizations
ND3
ltPgt¼85
NH3
ltPgt¼ 30-40
3He
ltPgt¼ 65
8
Inclusive Scattering
1st order Feynman diagram
Kinematics
Q2 4-momentum transfer X Bjorken Scaling
var W Invariant mass of target

deviation from point-like behavior characterized
by the Structure Functions
Inclusive Cross Section
9
Inclusive Scattering
1st order Feynman diagram
Kinematics
Q2 4-momentum transfer X Bjorken Scaling
var W Invariant mass of target

deviation from point-like behavior characterized
by the Structure Functions
Inclusive Cross Section
10
Inclusive Scattering
When we add spin degrees of freedom to the
target and beam, 2 Addiitonal SF needed.

all four SF needed for a complete description of
nucleon structure
Inclusive Polarized XS Differences
11
Generalized Sum Rules
Ji and Osborne, J. Phys. G27, 127 (2001)
Unsubtracted Dispersion Relation Optical
Theorem
Extended GDH Sum
BC Sum Rule
Superconvergence relation valid at any Q2
Relies on the virtual Compton scattering
amplitude S2 falling to zero faster than 1/º as
º ? 1
GDH Sum Rule at Q20 Bjorken Sum Rule at Q21
Free from QCD rad. corrections TMC
PLB 345 (1995) 527
12
Generalized Forward Spin Polarizabilities
Drechsel, Pasquini and Vanderhaehen, Phys. Rep.
378, 99 (2003).
LEX of gTT and gLT lead to the Generalized
Forward Spin Polarizabilities
x2 weighting dominated by RR
Ideal quant to test chiPT
13
Status of World Data
Very Well Known
14
Status of World Data
Very Well Known
g1 pretty well known
15
Proton g1
Sebastian Kuhn, DIS09
0.06ltQ2lt4.5
16
First moments of g1p
Extended GDH Sum Rule
Bjorken Sum Rule
GDH sum rule Bjorken sum rule higher twist effects
Sebastian Kuhn, DIS09
17
World g2p Data
SLAC ltQ2gt 5 GeV2
xg2
Only a single Q2 point!
18
World g2p Data
SLAC ltQ2gt 5 GeV2
JLAB ltQ2gt 1.3 GeV2
arXiv0812.0031
xg2
RSS Preliminary
K.S. and O. Rondon et al. arXiv0812.0031
Doubles the World Q2 Coverage ?
19
New Data From JLab
Thanks to the spokesmen of these
experiments! RSS Mark Jones, Oscar
Rondon E01-012 Nilanga Liyanage, J.P. Chen,
Seonho Choi SaGDH J.P. Chen, A. Deur, F.
Garabaldi
20
BC Sum Rule
Existing World Data on ?2
P
BLACK E94010. (Hall A, 3He)
N
BROWN E155. (SLAC NH3,6LiD)
3He
Note
SLAC Measured 0.02 lt x lt 0.8
JLAB Measured Resonance Region
W lt 2 GeV
21
BC Sum Rule
BRAND NEW DATA!
P
Very Preliminary
RED RSS. (Hall C, NH3,ND3)
K.S., O. Rondon et al. arXiv0812.0031
BLUE E01-012. (Hall A, 3He)
N
P. Solvignon et al in preparation
GREEN E97-110. (Hall A, 3He)
Courtesy of V. Sulkosky
3He
22
BC Sum Rule
What can BC tell us about Low-X?
P
Alternatively, if we assume BC holds we can
learn something about the unmeasured part of
Integral
ELASTIC
N
BC 0 gt Res Elas DIS
Unmeasured Low-x part
DIS -(RESELAS)
23
BC Sum Rule
0ltXlt1 Total Integral
P
BC RESDISELASTIC
RES Here refers to measured x-range
N
DIS refers to unmeasured low x part of the
integral. Not strictly Deep Inelastic
Scattering due to low Q2 Assume Leading Twist
Behaviour
Elastic From well know FFs (lt5)
24
BC Sum Rule
P
BC satisfied w/in errors for JLab Proton 2.8?
violation seen in SLAC data
N
BC satisfied w/in errors for Neutron
(But just barely in vicinity of Q21!)
25
BC Sum Rule
Proton g2p still relatively unknown for such a
fundamental quantity.
P
Wasteland
N
26
BC Sum Rule
Proton g2p still relatively unknown for such a
fundamental quantity.
P
Future Sane Just completed! 2.3 lt Q2 lt 6
GeV2 g2p in Hall A, 2011 0.015 lt Q2 lt 0.4
GeV2
N
27
BC Sum Rule
What can BC tell us about Low-X?
P
N
Unmeasured Low-X
DIS -(RESELAS)
28
Higher Twists
29
CN Moments
Cornwall Norton Moments
Superscript conventionally dropped for n1
Most analysis of SSF historically performed in
terms of the CN moments.
30
Operator Product Expansion (OPE) Expansion of SF
moments in powers of 1/Q2 (twist)

Leading Twist maps to the reliable predictions
of the parton model.
Higher Twists non-perturbative multiparton
interaction and non-zero quark masses.
Confinement
31
Operator Product Expansion (OPE) Expansion of SF
moments in powers of 1/Q2 (twist)

Leading Twist maps to the reliable predictions
of the parton model.
Higher Twists non-perturbative multiparton
interaction and non-zero quark masses.
Confinement
32
Operator Product Expansion (OPE) Expansion of SF
moments in powers of 1/Q2 (twist)

Leading Twist maps to the reliable predictions
of the parton model.
Higher Twists non-perturbative multiparton
interaction and non-zero quark masses.
Confinement
33
Accessing Higher Twists
Cornwall Norton Higher Moments
Standard approach
only approximate... more on this later.
I(Q2) ? the twist-3 matrix element. Ignores
terms of order M2/Q2
Y.B. Dong PRC 77, 015201 (2008)
34
I(Q2)
Existing World Data on I(Q2)
PROTON
BLACK E94010
M. Amarian, et al. PRL. 92 (2004) 022301
BROWN E155
P.Anthony, et al. PLB. 553 (2003) 18
RED RSS.
Wesselman, Slifer, Tajima et al. PRL
98(2007)132003.
Magenta E99-117
X. Zheng et al. PRC 70(2004)065207
NEUTRON
35
I(Q2)
BRAND NEW DATA!
MAID Model
Very Preliminary
RED RSS. (Hall C, NH3,ND3)
K.S., O. Rondon et al. arXiv0812.0031
BLUE E01-012. (Hall A, 3He)
P. Solvignon et al in preparation
NEUTRON
GREEN E97-110. (Hall A, 3He)
Courtesy of V. Sulkosky
stat only
36
I(Q2)
QCDF Group
Osipenko et al. PRD. 71 (2005) 054007
Shaded Region Estimate of I(Q2) Large
uncertainty due to lack of knowledge of g2p
stat only
37
Accessing Higher Twists
Cornwall Norton Higher Moments
I(Q2) ? the twist-3 matrix element. Ignores
terms of order M2/Q2
Y.B. Dong PRC 77, 015201 (2008)
38
Accessing Higher Twists
Cornwall Norton Higher Moments
I(Q2) ? the twist-3 matrix element. Ignores
terms of order M2/Q2
Y.B. Dong PRC 77(2008) 015201
Very significant below Q25
Y.B.Dong PLB 653,(2007)18
39
Nachtmann Moments
Nachtmann Moments
Matsuda Uematsu, N.Phys. B168(1980)181
Piccione Ridolfi N. Phys. B513(1998)301
Y.B. Dong PRC 77(2008) 015201
40
Nachtmann Moments
Nachtmann Moments
Matsuda Uematsu, N.Phys. B168(1980)181
Piccione Ridolfi N. Phys. B513(1998)301
Y.B. Dong PRC 77(2008) 015201
Generalization of CN moments to protect from the
TMC
Reduces to familiar form
Not a new idea, but difficult to implement unless
g2 measured simultaneously with g1
41
RSS Experiment
Measured g1 and g2 at Q2 1.3 GeV2
K. S., O. Rondon, et al arXiv0812.0031
Nachtmann moment reveals twist-3 at more
than 3 sigma significance.
42
RSS Experiment
Measured g1 and g2 at Q2 1.3 GeV2
K. S., O. Rondon, et al arXiv0812.0031
Nachtmann moment reveals twist-3 at more
than 3 sigma significance. CN
moment overestimates twist-3 by about 50 !
43
RSS Experiment
Measured g1 and g2 at Q2 1.3 GeV2
K. S., O. Rondon, et al arXiv0812.0031
Nachtmann moment reveals twist-3 at more
than 3 sigma significance. CN moment
overestimates twist-3 by about 50 !
R-gt1 in case of vanishing nucleon mass
R always less than 1 gt I(Q2) overestimates
twist-3
44
Generalization of G1
Matsuda Uematsu, N.Phys. B53(1998)301
Piccione Ridolfi N. Phys. B513(1998)301
Proton
Osipenko et al. PRD 71, 054007 (2005)
Global analysis of g1p data. Allows to cleanly
extract leading twist term.
TMC not as large as for I(Q2)
45
Spin Polarizabilities
46
Forward Spin Polarizabilities
Major failure of chiPT calcs.
Proton
Y. Prok et al. Phys. Lett. B672 12, 2009
47
Forward Spin Polarizabilities
Similar problem for Neutron
PRL 93 152301 (2004)
Add by hand major effect for 0 but not for
LT
Relativistic Baryon ÂPT Bernard, Hemmert,
Meissner PRD 67076008(2003)
Heavy Baryon ÂPT Calculation Kao, Spitzenberg,
Vanderhaeghen PRD 67016001(2003)
48
Future JLab Proton Data
The Hall B Eg4 Experiment The Hall A g2p
Experiment The Hall C SANE Experiment
49
EG4 g1p
E08-027 g2p
0.01 lt Q2 lt 0.5 GeV2 Resonance Region
Hall B Proton and Deuteron Ran in 2006 Under
analysis
Hall A Proton Will Run in 2011
50
Extended GDH Sum Rule
51
Burkhardt-Cottingham Sum Rule
Extended GDH Sum Rule
52
E08-027
SANE
Twist-3 Matrix Element
53
E08-027
SANE
Twist-3 Matrix Element
LT Spin Polarizability
54
Summary
BurkhardtCottingham Sum Rule Good coverage for
Neutron. Proton g2p is still relatively
unknown. Data seems to validate BC Assuming BC
holds, we can use JLab data to say something
about low-x. Target Mass Effects TMC are
significant at JLab kinematics Nachtmann moments
protect the SSF from TMC Must use Nachtmann
Moments in order to cleanly extract Higher
twists JLab 6 GeV Program Still lots of good
Spin Physics to be completed before the
upgrade. SANE d2n g2p E08-027 EG4
55
Hydrogen Hyperfine Structure
NCG PRL 96 163001 (2006)
Structure Dependent
Inelastic
Elastic Scattering
56
Hydrogen Hyperfine Structure
This experiment
NCG 2006 Used CLAS model assuming 100 error
Integrand of 2
Assuming this uncertainty is realistic we will
improve this by order of magnitude
But, unknown in this region
Dominated by this region due to Q2 weighting
MAID Model
Simula Model
So 100 error probably too optimistic We will
provide first real constraint on 2
57
backups
58
ELT Sum Rule
Efremov, Leader and Teryaev (ELT) Sum Rule
for the valence quark contribution to the SSF
2nd equality assumes that the sea quark
distributions are isospin independent
RSS experiment result at Q21.28 GeV2
Resonance Region only
Total Integral
DIS contribution dominates
59
g2 Structure Function
Wandzura-Wilczek relation
PLB 72 (1977) 195

Leading twist determined entirely by g1
Higher twist
g2 doesnt exist in Parton Model. Good quantity
to study higher twist
60
Neutron Extraction
Correcting for the D-state contribution.
Integrating over the fermi motion and binding
effects.
For Integrated Quantities
D ?d(Proton Neutron)
good to a few percent at low Q2
?d 0.925 0.015
Kulagin and Melnitchouk PRC 77, 015210 (2008).
3He PN Neutron 2PP Proton
good to 5 down to Q2 0.5 GeV2
C. Cio? degli Atti and S. Scopetta, Phys. Lett.
B404, 223 (1997).
PN 0.86 0.02 PP -0.028 0.004
Need for more sophisticated method at very low Q2
61
BC Sum Rule
Neutron results around Q21.3 GeV2 from 2 very
different experiments RSS in Hall C Neutron
from ND3 NH3 E01-012 in Hall A Neutron from
3He
P
N
Excellent agreement! for neutron from ND3 and 3He
3He
62
Existing DIS g2 Data
Jlab Hall A x¼0.2
SLAC ltQ2gt 5 GeV2
Proton
Neutron
Deuteron
63
Existing Resonance g2 Data
Q21.3
Q2
3He g2 (Jlab Hall A)
g2ww
Lowest Q2 Existing Proton Data
(Jlab Hall C RSS)
64
BC Sum Rule
Unmeasured Contributions
ELASTIC X1
Low-X Estimate
Assume g2g2WW at low x.
Supported by RSS data
15 variation seen depending on choice of g1
used.
(Form Factor uncertainties less than 5)
65
BC Sum Rule
What can BC tell us about Low-X?
P
Alternatively, if we assume BC holds we can
learn something about the unmeasured part of
Integral
ELASTIC
N
BC 0 gt Res Elas DIS
Unmeasured Low-x part
3He
DIS -(RESELAS)
66
I(Q2)
E08-027 g2p
SANE
Upcoming 6 GeV Experiments Sane Fall 2008 2.3
lt Q2 lt 6 GeV2 g2p in Hall A, 2011 0.015 lt Q2
lt 0.4 GeV2
projected
d2n in Hall A, 2009
Q2 3 GeV2
67
Polarized Ammonia Target
Dynamic Nuclear Polarization of NH3 and ND3
5 T field Split Helmholtz pair superconduct
magnet 1K 4He evaporation refrigerator
Cooling power about 1 W Microwave Power 1W at
140 GHz to pump electrons
Insulated cryostat 85 L Liquid He resevoir 57
L Liquid N shield (300K BB shield)
JLab Hall C configuration
68
Polarized 3He
Polarized 3He Target in Hall A